Mixtures of diazonium compounds and carboxylated polymers in the making of a light-sensitive lithographic plate



3 544 317 in US. Pat. No. 2,772,972, the reaction product of potas- MIX sium ferrocyanide and a diazo compound described in i g f g i US. Pat. No. 3,113,023, and the reaction compound of mo OF A LIGHT-SENSITIVE LITHOGRAPI HC the P p oxygenated anion f a p ly- PLATE or an isopoly-acid described in Japanese Pat. No. 7,663/

Teruhiko Yonezawa, Kanagawa, Japan, assignor to 5 y r p Corporation, Yonkers, It has now been found that a mixture of a polymer hav- N0 P g- Flled 9 1966, 601,848 ing carboxyl groups and diazonium is very effective as a Claims Priority, 1 1 2331??? gz 1965 light-sensitive material capable of making positive-acting Int. CL G0 7/2)} G03: 1/52 10 printing plates. That is, the present invention is concerned CL 96 33 10 Claims with positive-acting prmtmg plates contammg such a mixture in the light-sensitive layer thereon.

Polymers having carboxyl groups to be used in the present invention can be addition 01 merization 01 ABSTRACT OF THE DISCLOSURE mers obtained by the copolyrfaer ization of a r i l m satii- A light-sensitive composition which comprises a mixfated ethylene p nd having a carboxyl group or ture of a polymeric material having a molecular weight g p at the oe-positiml 0f the sh-P 0f the of b tw en b t 10,000 and 100,000 nd having carboxyl pound, for example, acrylic acid, methacrylic acid, acroylgroups thereon, said polymeric material being substany y acid, maleic hy itacollic acid, tially insoluble in a solution of equal parts of water and tenie aeid and vinyl benzoate, with one or more other isopropyl alcohol and being slightly swelled by said solu- Saturated ethylene compounds, or can he condensation tion without substantial decrease of its film strength, and p ym rization ype polymers shown in the following a light-sensitive diazonium compound; and positive-actformulas; ing lithographic printing plates having said light-sensitve composition coated on a supporting base. NHCO0(CHa)20CO oooH COOH .i:

om I L 0 OH 0 on CH3 is (11 2: (III) The present invention relates to a printing plate endowed with light sensitivity for making a positive print- I ing plate by light exposure through a transparent or trans- 1 lucent positive original or pattern.

A diazonium compound, for example, a diazonium salt of p-amino-diphenylamine or a formaldehyde-con- J densate thereof, which has hitherto been known as a COOH x (IV) light-sensitive material for lithographic printing plates, is or can be a high-molecular weight compound such as converted when struck by light into an ink-receptive comcarboxyl methyl cellulosein whicha carboxyl group has pound while the unexposed diazonium compound 15 easily been ntroduced by chemlcal reaction. That is, the polydissolved with water or an aqueous solution of an acid mers include naturally occurring or synthetic high-molecor gum arabic. Therefore, a hydroph lic surface thereof ular weight compounds havmg carboxyl groups. Further, can be used for making a pos tive pnnt ng plate by exthe carboxyl group of such a high-molecular weight compfstlriathrough 2111 negatrvergrigmal or platterrlll. gr pr nting plfundfmay be the sodium, potassium or ammonium salt p a vmg suc a prope 1s genera y ca e a negaereo tive-acting plate. On the other hand, there are light-sen- The most important property of such a polymer that sitive compounds which have an ink-receptive property determines whether it can practically be used on a posithat can be converted into ahydrophihc compoundwhen trve-acting printing plate is its water solubility. That is, struck by hght. hydrophilic plate having a coating of a polymer that contams enough carboxyl groups so that such a light-sensitive compound on the hydrophilic surwhen it is mixed with a diazonium salt the mixture is face can be used for making a pos tive printing plate easily dissolved inwater cannot practically be used, while by exposure through a positive origmal or pattern. A a polymer showing little or no hydrophilic property also pr i ntmg plate havmg such a property is generally called cannot be used. A practically adoptable measure of the a li g lft z h s ifi terials for providing positive act ll d ii zn c l b grcghlps in li iii ii a t li era y e e ecause enum er 1s uenc y e ing printing plates there are ortho-diazoquinones described drophilic property of portions of the polymer other tha n the carboxyl groups. The polymer, however, must conbut does not lose its strength as a film or a coating, and

(2) The polymer is not dissolved by that solution.

The molecular weight of the polymer can vary over a considerably wide range and influences the kind of solvent for the polymer, the solubility of the polymer in the solvent and the viscosity of thesolution of the polymer. The molecular weight also largely influences the speed of development of a light-sensitive printing plate containing thepolymer, the adhesive strength of the image to the support, the sharpness of image and the length of the presslife of the printing plate. The optimum molecular weight varies according to the type of polymer, and is preferably from about 10,000 to about 100,000.

Diazonium compounds having many structures can be employed in the present invention, but a condensation product of formaldehyde and a diazo compound of paminodiphenylamine, preferably one that has been stabilized with zinc chloride, is especially suitable. To improve the solubility of that condensation product in organc sol vents, it can be further reacted with p-toluene sulfonic acid, ammonium fluoroborate or ammonium hexafluorophosphate.

The mixing ratio of the carboxyl-containing polymer to the diazonium salt can be within the range of about 50:1 to about 5:1. The mixture is dissolved in a suitable aqueous or organic solvent, for example, methyl ethyl ketone, Cellosolve, dimethyl formamide, dimethyl sulfoxide, dioxane, cyclohexane, water or a mixture thereof and the solution is applied to a supporting base such as a metallic plate that has previously been treated by processes as described in, for example, Japanese Pat. No. 22,063/61, US. Pat. No. 2,995,443, British Pat. No. 907,002, US. Pat. No. 3,130,051, U.S. Pat. No. 3,163,534, Japanese Pat. No. 706/59 and Japanese Pat. No. 23,982/64. The supporting base can be paper or plastic; a suitable metallic plate can be of aluminum, zinc, tin, copper and the like. Into the coating solution can be incorporated a surfaceactive agent, a pigment, a dye or fillers such as colloidal silica, clay or white carbon. The addition of a surfaceactive agent improves the wetta-bility of the coating solution on the metallic plate or paper, the addition of pigment or dye makes the developed image easily perceivable, and the addition of fillers influences the removability of the coating at development and the physical strength of the image.

The amount of the coating is suitably about 0.01 to 2 g./sq. m., after drying, and the coated plate or sheet can be dried by hot air or by infrared irradiation by means such that the surface temperature remains at less than about 100 C. A positive-acting lithographic printing plate is thus obtained.

In general when a film composed of a mixture of a naturally occurring or a synthetic high-molecular weight material and a diazonium salt is struck by light, the film becomes insoluble in a solvent because free radicals formed during the photo-chemical decomposition of the diazonium salt cause reaction among the molecules in the high molecular weight chains to provide a three-dimensional structure, i.e., crosslinking. Therefore,'in such a conventional case, the unexposed portions can be removed with a solvent, leaving only the exposed portions.

On the otherhand, in the coatings formed by mixtures of carboxylic acid polymers and diazonium salts according to the present invention, the exposed portions can be removed from the lithographic printing plate by a solvent for the polymers diluted with a non-solvent. The mechanism is not yet clear but it presently is considered that the high-molecular weight chains are broken by light irradiation and, as a result of the formation of three-dimensional structures, the adhesion of the coating will be substantially reduced in the mixed system of solvent and non-solvent.

A positive-acting lithographic printing plate according to this invention can be used as follows:

(1) Exposure: A lithographic printing plate of this invention was placed together with a positive film and was exposed for 2 minutes by means of a 30 amp. carbon are at a distance of 70 cm. from the light source. Suitable exposure was obtained by using a gray scale of LTF of 21st step until the film of 4th step was completely removed.

(2) Development: The exposed surface of the printing plate was rubbed lightly with an absorbent cotton wad or a velvety brush impregnated with a developing solution having the following composition to remove the exposed portions of the light-sensitive film:

Parts Water 2 Ethyl acetate 1 Isopropyl alcohol 1 Diacetone alcohol 0.5

(3) Application of developing ink: A standard lithographic developing ink, Developing Ink No. 801 (made by Fuji Photo-Film Co. of Japan, was applied to the'developed printing plate surface by means of a cellulose sponge.

(4) Gum coating: A dilute aqueous solution of gum arabic was applied to the surface of the developed plate and dried.

Printing plates processed as described reproduce 50,000 to 100,000 copies on standard lithographic printing machines. During press runs no contamination of the plates was observed and the sharpness of the images was very good.

Another feature of the present invention is that the storage life of lithographic printing plates according to this invention is long. In general diazonium salts e unstable to water. The diazonium salts used in this invention, however, are protected by the resin and hence are prevented from being contacted directly with moisture in the air, and the printing plates of this invention can be preserved stably for at least about one year. Furthermore, as mentioned above, the printing plates of this invention can be used easily without the necessity of special skills and, because the image is composed of a resin, it is unnecessary to strengthen the image by applying a lacquer to it.

The principle of the present invention can, of course, be applied not only to lithographic printing but also to relief printing, intaglio printing and other methods of printing.

fonic acid 1 Methanol Cellosolve acetate Pigment red 17 (made by Sumitomo Chemical 'was passed through a colloid mill to prepare a uniform solution which was applied to an aluminum plate, the surface of which had been processed by the method described in US. Pat. 2,946,683, and dried. The quantity coated was 0.8 g./ sq. m. After drying sufficiently, a positive image was printed on the plate by exposure through a positive film. The printing plate was then developed by removal of the exposed portions of the coating, a developing ink was applied and the plate was coated with gum arabic. The plate thus obtained was run on a Heidelberg ofiset printing press, and it produced 100,000 copies.

EXAMPLE 2 A mixture of: Parts Copolymer of vinyl acetate (85%), ethyl acrylate (11%) and crotonic acid (4%) Formaldehyde condensate of p-diazodiphenylamine and ammonium fluborate Cellosolve acetate 80 Methyl ethyl ketone 15 Diacetone alcohol 15 Cyania blue 2 was mixed in a ball mill for about hours. The resulting solution was applied to an aluminum plate, which had been subjected to a surface treatment by the method described in US. Pat. No. 2,946,683, and then dried by an infrared heater. The amount coated was 2 g./sq. m. The lithographic printing plate thus prepared provided very good results.

I claim: 1

1. A light-sensitive composition which comprises a mixture of polymeric material having a molecular weight NH-Q-Q-NHCOMCH to o 0 l 0 OH 0 OH .L (I) parts by weight of said polymeric material per part of said diazonium compound.

5. A light-sensitive positive-acting lithographic printing plate which comprises a supporting base and coated thereon a light-sensitive composition which comprises a mixture of a polymeric material having a molecular weight of between about 10,000 and 100,000 and having carboxyl groups thereon, said polymeric material being substantially insoluble in a solution of equal parts of water and isopropyl alcohol and being slightly swelled by said solution without substantial decrease of its film strength, and said polymeric material being (1) an addition polymer obtained by copolymerization of an ethylenically unsaturated compound having at least one carboxyl group at the alphaor alpha, betapositions with another ethylenically unsaturated compound, (2) a condensation polymer of the formula LN Q I. I 0 OH OOH r 1 NH- cn=on NHoo0--o-o o o-- CH: J

0 0H 0 on x (II) I NHCO OH; 0 C ONH L 3 CH;

O OH O OH OH I -CH L CO OH-IX wherein said composition contains from about 5 to about or (3) a carboxy alkyl cellulose, and a light-sensitive diazonium compound.

6. A light-sensitive positive-acting lithographic printing plate acording to claim 5 wherein said diazonium compound is selected from the group consisting of a condensation product of p-diazodiphenylamine and formaldehyde, p-diazodiphenylamine and formaldehyde stabilized with zinc chloride, and p-diazodiphenylamine and formaldehyde reacted with p-toluene sulfonic acid, ammonium fiuoroborate or ammonium hexafluorophosphate.

7. A light-sensitive positive-acting lithographic printing plate according to claim 5 wherein said diazonium compound is a condensation product of formaldehyde and a diazo compound of p-amino-diphenylamine.

8. A light-sensitive positive-acting lithographic printing plate according to claim 5 wherein said composition contains from about 5 to about 50 parts by weight of said polymeric material per part of said diazonium compound.

9. A light-sensitive composition according to claim 1 wherein said ethylenically unsaturated compound (1) is acrylic acid, methacrylic acid, acroylhydroacrylic acid,

maleic anhydride, itaconic acid, crotonic acid or vinyl benzoate.

10. A light-sensitive posiitve-acting lithographic printing plate according to claim -5 wherein said ethylenically unsaturated compound 1) is acrylic acid, methacrylic acid, acroylhydroacrylic acid, maleic anhydride, itaconic acid, crotonic acid or vinyl benzoate.

3,383,211 5/1968 Poels et al. 96-29 3,235,382 2/ 1966 Neugebauer 9'6-33 3,211,553 10/1965 Ito 96-75 3,166,421 1/ 1965 Gramlich 9 6-49 DONALD LEVY, Primary Examiner M. B. WITIENBERG, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 544 317 D e c emb e l9l Inventor($) Teruhiro Yonezawa It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C01. 3, line 24, change "organc" to organic Claim 5, formula (III), change "CH to CH thus I CH NIARZ I97] Anew ward M. Fletcher, I1". WILLIAM E. 38- 0mm oomissioner or Patents 

